Kazmir used to be a Met too, was traded for Victor Zambrano. The Mets are notorious for blowing up the farmsystem with worthless trades.
Besides the Kazmir trade, which was made by an interim GM who lost his job after 2 months, and the Bay trade in 2002, (the Mets, along with the Expos and Padres, traded Bay before he was seen as a top prospect) is there another instance of a traded Mets prospect making it big? No.
Carlos Gomez? Solid player, but traded for Johan Santana. Mets Win.
Lastings Milledge? No.